A great deal is known about many drugs, how they act and where they localize in the body. Investigators have sought many ways of utilizing this information so the drugs may be made into radiopharmaceuticals and used in the diagnosis of disease. In this project a new method has been devised, which from preliminary data appears successful. Chemicals, known as chelates which bind metal ions have been incorporated into drug molecules to create synthetic analogs of the drugs. The metal ions used are specially chosen radioisotopes which allow the distribution of the radiolabelled molecule (radiopharmaceutical) in the body to be recorded as an image, thus visualizing the target organ and observing its function. The drugs chosen are ones known to accumulate in the heart and certain forms of cancer. Successful completion of this work will be of value in the diagnosis of heart disease and cancer. BIBLIOGRAPHIC REFERENCES: M.D. Loberg and A. Fields. Stability of 99m Tc-Labeled N-substituted Iminodiacetic Acids: Ligand Exchange Reaction Between 99m Tc-HIDA and EDTA. Accepted for publication in International Journal of Applied Radiation Isotopes. 1977, in press. J. W. Ryan, M.D. Cooper, M.D. Loberg, E.B. Harvey, and S. Sikorski. 99m Tc-HIDA for Hepatobiliary Studies. Accepted for publication Journal of Nuclear Medicine - 1977, in press.